The present invention relates to a content-based image retrieval system and a method for retrieving an image using the same; and, more particularly, to a content-based image retrieval system and a method for retrieving an image based on an angular radial transform (ART) image descriptor.
As Internet techniques have developed and use of multimedia data is increased in rapid, an image retrieval based on a text cannot guarantee reliability in results of the retrieval. To solve the problem as mentioned above, an image retrieval based on an image is performed.
The image retrieval based on the image means a method for finding an image (or images) similar to a query image by extracting an image descriptor describing a characteristic of the image from the image; and measuring a similarity between an image descriptor of the query image inputted by the user and that of an image stored on a database. The image descriptor includes a color descriptor, a texture descriptor and a shape descriptor, which respectively describes a color of the image, a texture of the image and a shape of the image. An efficiency of the image retrieval system depends on how much image descriptor efficiently describes characteristics of the image.
A moment descriptor is mostly used as a conventional shape descriptor. The moment descriptor is invariant to a size, a movement and a rotation of the image.
To obtain the moment descriptor of the input image, first, an edge extraction is processed. In other words, an object of the image is separated from a background. The image data is converted to binary data. Then, an outer boundary line of the object is extracted from the separated background and a shape vector of the object is obtained from the separated object.
In order to measure a similarity between the input image and an image stored on a database, a Euclidean distance measurement method is used. The Euclidean distance measurement method is expressed as following equation (1).                                                                         D                ⁡                                  (                                      q                    ,                    t                                    )                                            =                                                                    (                                                                  H                        q                                            -                                              H                        t                                                              )                                    T                                ⁢                                  (                                                            H                      q                                        -                                          H                      t                                                        )                                                                                                        =                                                ∑                                      m                    =                    0                                    M                                ⁢                                  (                                                                                    H                        q                                            ⁡                                              [                        m                        ]                                                              -                                                                  H                        t                                            ⁡                                              [                        m                        ]                                                                              )                                                                                        (        1        )            
where, q is an input image, t is an image stored on a database, Hq is a moment value of the input image q, Ht is a moment value of the image stored on the database and M is an integer number between 0 and 6.
In the conventional content-based image retrieval system based on the moment descriptor, since the polynomial function used as a basis function is not orthogonal, extracted moment values, which are descriptors, are overlapped. Accordingly, an efficiency of the descriptor is low, and the descriptor cannot represent characteristics of the image, which are recognized by a user. Accordingly, the conventional content-based image retrieval system has a serious problem in that it cannot retrieve a similar image.
In order to solve the problem as mentioned above, some content-based retrieval systems based on a Zernike moment are developed. One of them is described in a pending U.S. patent application Ser. No. 09/203,569 filed on Dec. 2, 1998, xe2x80x9cMethod for Automatic Retrieval of Device-Mark Type Trademark Images Based upon Content of Trademarkxe2x80x9d.
The Zernike moment has an orthogonal value, however, may not effectively represent characteristics of the image in a radial direction. Accordingly, the conventional content-based image retrieval system based on the Zernike moment cannot perform an accurate image retrieval.
Therefore, it is an object of the present invention to provide a content-based image retrieval system and a method for retrieving image using the same, which are possible to search more similar image to a query image within a shorter time.
In accordance with an aspect of the present invention in order to obtain the object, there is provided a method for constructing a database storing images and image descriptors representing characteristics of the images, the method comprising the steps of: a) receiving an image; b) extracting an image descriptor from the image based on at least an angular component and a radial component of the image; c) storing the image on an image database; and d) storing the image descriptor on an image descriptor database.
In accordance with another aspect of the present invention, there is provided a method for retrieving an image in a content-based image retrieval system including a web browser, a web server and a database storing images and image descriptors each of which represents characteristics of the image, the method comprising the steps of: a) receiving a query image; b) requesting to retrieve an image based on a query image descriptor to the web server, the query image descriptor being extracted from the query image based on at least an angular component and a radial component of the query image; and c) receiving and displaying at least an image similar to the query image from the database.
In accordance with further another aspect of the present invention, there is provided a method for retrieving an image in a content-based image retrieval system including a web browser, a web server and a database storing images and image descriptors each of which represents characteristics of the image, the method comprising the steps of: a) receiving a query image from the web browser; b) extracting a query image descriptor from the query image based on at least an angular component and a radial component of the query image; c) comparing the query image descriptor with a plurality of image descriptors stored on the database, wherein the image descriptor is based on at least an angular component and a radial component of the image; d) arranging the image descriptors in order of a similarity to the query image descriptors; and e) allowing the database to provide at least an image similar to the query image to the web browser.
In accordance with still further another aspect of the present invention, there is provided a method for retrieving an image from a database storing images and image descriptors representing characteristics of the images, the method comprising the steps of: a) receiving a query image; b) extracting a query image descriptor from the query image based on at least an angular component and a radial component of the query image; c) comparing the query image descriptor with an image descriptor stored on the database; and d) determining a degree of a similarity between the query image descriptor and the image descriptor stored on the database.
In accordance with still another aspect of the present invention, there is provided a method for retrieving an image from a database storing images and image descriptors representing characteristics of the images, the method comprising the steps of: a) receiving a query image; b) extracting a query image descriptor from the query image based on at least an angular component and a radial component of the query image; c) comparing the query image descriptor with an image descriptor stored on the database; and d) determining a degree of a similarity between the query image descriptor and the image descriptor stored on the database.
In accordance with still another aspect of the present invention, there is provided data stream for use in retrieving an image, the data stream transmitted from a web browser to a web server, comprising: a retrieval request signal; and an image descriptor extracted from an image based on an angular component and a radial component of the image.